1. Field of the Invention
The present invention relates to a method of forming bumps which are electrical, mechanical, and thermal connection points to an object such as a semiconductor device or the like, and a system therefor.
2. Description of the Related Art
There are already many methods of forming bumps to a semiconductor device. They include, for example, a plating method in which metal is precipitated on the pads of a semiconductor device by a plating technology to form bumps (related art 1), a printing method in which solder paste is printed on the pads of a semiconductor device and is heated to melt solder particles in the solder paste and in which the solder particles is then solidified on the pads to form bumps (related art 2), and a stud bump method in which one end of a gold wire is bonded to a pad and in which the gold wire is then cut to form a bump (related art 3).
Further, the following methods have been known as related arts of forming bumps by the use of solder balls: first, solder balls are vacuum-sucked by a suction jig, then mounted on the surfaces of the pads of a semiconductor device, then melted by heating, and then solidified, which is disclosed in the specification and the drawings of U.S. Pat. No. 5,284,287 (related art 4); and, secondly, solder balls are vacuum-sucked by the use of a net plate, then mounted on the pads of a semiconductor device, then melted by heating, and then solidified, which is disclosed in Japanese Patent Publication No. 2,897,356 (related art 5).
However, the above-mentioned related arts have the following problems. In general, as the volume of a bump becomes larger, a semiconductor can have a longer connection life when it is connected to an electronic circuit substrate.
However, it is difficult in principle to form a bump having a sufficient volume by the plating method or the printing method (the related art 1 or 2). In addition, the plating method or the printing method presents a problem that when a semiconductor device is connected to an electronic circuit substrate, it is difficult to realize normal connections at all the bumps because the bumps have variations in height.
On the other hand, the stud bump method (the related art 3) presents a problem that it can be applied only to forming bumps made of a specific material such as gold because a wire is made of limited material. Also, the method present a problem that it takes much time to form the bumps in the case where the method is applied to manufacturing a semiconductor device having several tens of thousands of pads because the bumps are formed one by one.
Also, although the solder ball method (the related art 4 or 5) can form the bumps having a narrow range of variations in height and an adequate volume, it uses a jig for vacuum-sucking the solder balls, in which the jig has a complex structure and requires a technology of boring very small pores when the jig is manufactured. Since the jig becomes more expensive in proportion to the number of small pores, in the case where a semiconductor needs many bumps, the jig presents a problem of increasing cost in forming the bumps. Also, the method of using a net plate has an advantage that a jig becomes simple because only a hole having a large diameter in comparison with a solder ball is required to be made and because a net plate is used to prevent the solder balls from being sucked, but the method has a problem that, in the case where a solder ball is mounted above a net-wire of the net plate, the solder ball is sucked at a position shifted from the position where the solder ball is to be sucked.
In order to solve the problems of the above related arts, it is an object of the present invention to provide a method of forming many bumps having an adequate volume, a narrow range of variations in height, and few limitations in selecting material on an object such as a semiconductor device or the like at high production rates, with high reliability and with ease, and a system therefor.
Also, it is another object of the present invention to provide a method of forming bumps which can simplify a system constitution of forming many bumps on an object such as a semiconductor device or the like by one operation and can form bumps in large quantity, and a system therefor.
In order to accomplish the above objects, according to a first aspect of the present invention, there is provided a method of forming bumps, the method comprising the steps of: an alignment step of placing, on an alignment stage, a plate-like alignment jig having a group of apertures aligned in correspondence with positions where bumps are to be formed, and of sequentially charging many conductive particles supplied such as solder balls into the group of apertures of the plate-like alignment jig to align a group of conductive particles with respect to the plate-like alignment jig; a suction step of sucking and retaining the group of conductive particles aligned at the alignment step and the plate-like alignment jig for aligning the group of conductive particles by a suction unit to separate them from the alignment stage; a positioning step of moving the group of conductive particles and the plate-like alignment jig, both of which are sucked and retained at the suction step, above an object having a group of pads on which bumps are to be formed, and of positioning the plate-like alignment jig relatively to the object; a transfer step of relieving the group of conductive particles of suction and retention by the suction unit, in a state where the plate-like alignment jig positioned relatively to the object at the positioning step is placed close to the object, to transfer the group of conductive particles to the group of pads on the object; and a bonding step of bonding the group of conductive particles transferred at the transfer step to the group of pads on the object to form bumps.
Also, according to a second aspect of the present invention, there is provided a method of forming bumps as described above, in which the above-mentioned alignment step includes the steps of: placing, on an alignment stage, a plate-like alignment jig having a group of apertures aligned in correspondence with positions where bumps are formed; and moving a squeegee storing many conductive particles such as solder balls along the plate-like alignment jig from one end to the other end to sequentially charge the conductive particles into the group of apertures of the plate-like alignment jig to align a group of conductive particles with respect to the late-like alignment jig.
Also, according to a third aspect of the present invention, there is provided a method of forming bumps as described in the first aspect, in which the above-mentioned alignment step includes the steps of: placing, on an alignment stage, a plate-like alignment jig having a group of apertures aligned in correspondence with positions where bumps are to be formed; and moving a squeegee storing many conductive particles such as solder balls and having a sweeping member along the plate-like alignment jig from one end to the other end to sequentially charge the conductive particles into the group of apertures of the plate-like alignment jig, while sweeping away the extra conductive particles by the sweeping member, to align a group of conductive particles with respect to the plate-like alignment jig.
Also, according to a fourth aspect of the present invention, there is provided a method of forming bumps as described in the first aspect, in which the above-mentioned alignment step includes the steps of: placing, on an inclined alignment stage, a plate-like alignment jig having a group of apertures aligned in correspondence with positions where bumps are to be formed; and moving a squeegee storing many conductive particles such as solder balls and having a sweeping member along the inclined plate-like alignment jig from a higher position to a lower position to sequentially charge the conductive particles into the group of apertures of the plate-like alignment jig to align a group of conductive particles with respect to the plate-like alignment jig;
Also, according to a fifth aspect of the present invention, there is provided a method of forming bumps as described in the first aspect, in which the above-mentioned alignment step of: placing, on an inclined alignment stage, a plate-like alignment jig having a group of apertures aligned in correspondence with positions where bumps are to be formed; and moving a squeegee storing many conductive particles such as solder balls and having a sweeping member along the inclined plate-like alignment jig from a higher position to a lower position to sequentially charge the conductive particles into the group of apertures of the plate-like alignment jig, while sweeping away the extra conductive particles by the sweeping member, to align a group of conductive particles with respect to the plate-like alignment jig.
Also, according to a sixth aspect of the present invention, there is provided a method of forming bumps as described in the first aspect, in which the above-mentioned alignment step of: placing, on an inclined alignment stage, a plate-like alignment jig having a group of apertures aligned in correspondence with positions where bumps are to be formed; and moving a squeegee storing many conductive particles such as solder balls and having a sweeping member along the inclined plate-like alignment jig from a higher position to a lower position to sequentially charge the conductive particles into the group of apertures of the plate-like alignment jig based on the rolling motion of the conductive particles stored in the squeegee, while sweeping away the extra conductive particles by the sweeping member, to align a group of conductive particles with respect to the plate-like alignment jig.
Also, according to a seventh aspect of the present invention, there is provided a method of forming bumps as described in any one of the first to sixth aspects, further including an adhesive supply step of supplying an adhesive at least to the group of pads on the object such as a semiconductor device before the positioning step.
Also, according to an eighth aspect of the present invention, there is provided a method of forming bumps as described in any one of the first to sixth aspects, further including an inspection step of inspecting, after the alignment step, the state of the group of conductive particles aligned with the group of apertures of the plate-like alignment jig at the alignment step.
Also, according to a ninth aspect of the present invention, there is provided a method of forming bumps as described in any one of the first to sixth aspects, further including an inspection step of inspecting, after the alignment step, the state of the group of conductive particles aligned with the group of apertures of the plate-like alignment jig at the alignment step, and another alignment step executed in the case where the results of inspection at the inspection step reveal that the number of the apertures of the alignment jig which are not filled with the conductive particles exceeds the maximum permissible number.
Also, according to a tenth aspect of the present invention, there is provided a method of forming bumps as described in any one of the first to sixth aspects, further including an inspection step of inspecting, after the transfer step, the state of the group of conductive particles transferred to the group of pads on the object at the transfer step.
Also, according to an eleventh aspect of the present invention, there is provided a method of forming bumps as described in any one of the first to sixth aspects, further including an inspection step of inspecting, after the transfer step, the state of the group of conductive particles transferred to the group of pads on the object at the transfer step, and a repair step of selectively mounting the conductive particles on the pads on which the conductive particles are not mounted in the case where the results of inspection at the inspection step reveal that the number of the pads which are not mounted with the conductive particles exceeds the maximum permissible number, and of selectively removing the extra conductive particles in the case where the results of inspection at the inspection step reveal that the number of the extra conductive particles exceeds the maximum permissible number.
Also, according to a twelfth aspect of the present invention, there is provided a method of forming bumps as described in any one of the first to sixth aspects, further including a cutting step of cutting the object having bumps formed on the pads at the bonding step by a desired unit, after the bump forming step.
Also, according to a thirteenth aspect of the present invention, there is provided a system of forming bumps, the system comprising: an alignment unit for placing, on an alignment stage, a plate-like alignment jig having a group of apertures aligned in correspondence with positions where bumps are to be formed, and for sequentially charging many conductive particles supplied into the group of apertures of the plate-like alignment jig to align a group of conductive particles with respect to the plate-like alignment jig; a suction unit for sucking and retaining the group of conductive particles aligned by the alignment unit and the plate-like alignment jig for aligning the group of conductive particles to separate them from the alignment stage; and a transfer control unit for moving the group of conductive particles and the plate-like alignment jig, both of which are sucked and retained by the suction unit, above an object having a group of pads on which bumps are to be formed, and for positioning the plate-like jig relatively to the object, and for relieving the group of conductive particles of suction and retention by the suction unit, in a state where the plate-like alignment jig positioned relatively to the object is placed close to the object, to transfer the group of conductive particles to the group of pads on the object, wherein the group of conductive particles transferred by the transfer unit are bonded to the group of pads on the object to form bumps.
Also, according to a fourteenth aspect of the present invention, there is provided a system of forming bumps as described in the thirteenth aspect, in which the alignment unit places, on an alignment stage, a plate-like alignment jig having a group of apertures aligned in correspondence with positions where bumps are to be formed and moves a squeegee storing many conductive particles along the plate-like alignment jig from one end to the other end to sequentially charge the conductive particles into the group of apertures of the plate-like alignment jig to align a group of conductive particles with respect to the plate-like alignment jig.
Also, according to a fifteenth aspect of the present invention, there is provided a system of forming bumps as described in the thirteenth aspect, in which the alignment unit places, on an alignment stage, a plate-like alignment jig having a group of apertures formed in correspondence with positions where bumps are to be formed and moves a squeegee storing many conductive particles and having a sweeping member along the plate-like alignment jig from one end to the other end to sequentially charge the conductive particles into the group of apertures of the plate-like alignment jig, while sweeping away the extra conductive particles by the sweeping member, to align a group of conductive particles with respect to the plate-like alignment jig.
Also, according to a sixteenth aspect of the present invention, there is provided a system of forming bumps as described in the thirteenth aspect, in which the alignment unit places, on an inclined alignment stage, a plate-like alignment jig having a group of apertures aligned in correspondence with positions where bumps are to be formed and moves a squeegee storing many conductive particles and having a sweeping member along the inclined plate-like alignment jig from a higher position to a lower position to sequentially charge the stored conductive particles into the group of apertures of the plate-like alignment jig to align a group of conductive articles with respect to the plate-like alignment jig.
Also, according to a seventeenth aspect of the present invention, there is provided a system of forming bumps as described in the thirteenth aspect, in which the alignment unit places, on an inclined alignment stage, a plate-like alignment jig having a group of apertures aligned in correspondence with positions where bumps are to be formed and moves a squeegee storing many conductive particles and having a sweeping member along the inclined plate-like alignment jig from a higher position to a lower position to sequentially charge the stored conductive particles into the group of apertures of the plate-like alignment jig, while sweeping away the extra conductive particles by the sweeping member, to align a group of conductive particles with respect to the plate-like alignment jig.
Also, according to an eighteenth aspect of the present invention, there is provided a system of forming bumps as described in the thirteenth aspect, in which the alignment unit places, on an inclined alignment stage, a plate-like alignment jig having a group of apertures aligned in correspondence with positions where bumps are formed and moves a squeegee storing many conductive particles and having a sweeping member along the inclined plate-like alignment jig from a higher position to a lower position to sequentially charge the conductive particles into the group of apertures of the plate-like alignment jig based on the rolling motion of the conductive particles stored in the squeegee, while sweeping away the extra conductive particles by the sweeping member, to align a group of conductive particles with respect to the plate-like alignment jig.
Also, according to a nineteenth aspect of the present invention, there is provided a system of forming bumps as described in any one of the thirteenth aspect to the eighteenth aspect, further including a visual inspection unit for inspecting the state of the group of conductive particles aligned with the group of apertures of the plate-like alignment jig by the alignment unit.
Also, according to a twentieth aspect of the present invention, there is provided a system of forming bumps as described in any one of the thirteenth aspect to the eighteenth aspect, further including a visual inspection unit for inspecting the state of the group of conductive particles transferred to the group of pads on the object by the transfer control unit.
Also, according to a twenty-first aspect of the present invention, there is provided a system of forming bumps as described in any one of the thirteenth aspect to the eighteenth aspect, further including a visual inspection unit for inspecting the state of the group of conductive particles transferred to the group of pads on the object by the transfer control unit, and a repair unit for selectively mounting the conductive particles on the pads on which the conductive particles are not mounted in the case where the results of inspection by the visual inspection unit reveal that the number of the pads which are not mounted with the conductive particles exceeds the maximum permissible number, and for selectively removing the extra conductive particles in the case where the results of inspection by the visual inspection unit reveal that the number of the extra conductive particles exceeds the maximum permissible number.
Also, according to a twenty-second aspect of the present invention, there is provided a system of forming bumps as described in any one of the thirteenth aspect to the eighteenth aspect, in which the suction unit is. constituted by a vacuum suction unit.
Also, according to a twenty-third aspect of the present invention, there is provided a system of forming bumps as described in any one of the thirteenth aspect to the eighteenth aspect, in which the suction unit is constituted by a vacuum suction unit having a porous substrate at the portion where the group of conductive particles are sucked.
Also, according to a twenty-fourth aspect of the present invention, there is provided a system of forming bumps as described in any one of the fifteenth, seventeenth, and eighteenth aspects, in which the alignment unit has a sweeping member constituted by a plurality of flexible wires.
As described above, according to the above-mentioned constitution, it is possible to form bumps using conductive particles such as solder balls having an adequate volume, a narrow range of variations in height, and few limitations in selecting material, by one operation at high production rates with high reliability and with ease.
Also, according to the above-mentioned constitution, it is possible to simplify a system constitution for forming many bumps on an object such as a semiconductor device or the like by one operation and to form the bumps in large quantity.
Also, according to the above-mentioned constitution, it is possible to inspect the number of conductive particles such as solder balls and to replenish the conductive particles or to repair the arrangement thereof, if necessary, to thereby further improve reliability.